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Results for “Soft X-ray spectrometer”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The nearby interstellar medium

The high dispersion spectrometer on board the International Ultraviolet Explorer (IUE) satellite was used to observe interstellar absorption lines in Rasalhague (Alpha Oph). This star is located 18 pc from the sun in the direction of the North Polar Spur, a prominent radio continuum feature in the Ophiuchus region of the sky. The satellite results, combined with previous interstellar line data and observations of the 'local interstellar wind' and soft X-ray emission, support earlier suggestions that the sun is immersed in a supernova remnant which may be an extension of the 'Loop I' or 'North Polar Spur' supernova remnant seen in the Scorpius-Ophiuchus region of the sky.

Frisch, P. C.↗
NASA NTRS1986

A reflection grating spectrometer for the X-ray Multi-Mirror (XMM) space observatory - Design and calculated performance

Attention is given to a spectrometer design candidate for the X-ray Multi-Mirror observatory, being planned by the European Space Agency as a long-lived large-area array of telescopes. The science requirement of moderate resolution spectroscopy in a two octave region with extremely high throughput leads to the use of grazing incidence reflection gratings. It is noted that the sensitivity of the instrument is sufficient to permit the first spectral detection of soft X-ray features in external galaxies.

Hettrick, Michael C.↗
DOE OSTI2025

The meV-resolved Inelastic X-ray Scattering Beamline at NSLS-II: Design and Performance

The ultrahigh resolution inelastic X-ray scattering (IXS) beamline at NSLS-II is designed and built to achieve sub-meV resolution at a moderate energy of 9.13 keV for IXS experiments with high momentum resolution and high spectral contrast. The key instrument is a novel spectrometer featuring a new type of analyzer optics, which combines post-sample collimation with angular dispersive crystal optics. As the first user instrument of its kind, the spectrometer has demonstrated unique research capabilities in exploring low momentum transfer (Q), THz dynamics in soft material systems characterized by mesoscopic heterogeneity and complexity, such as liquid crystals and bio-membranes. Ongoing efforts to improve performance since the start of user operations have resulted in a state-of-the-art energy resolution in routine operations of less than 1.4 meV, with sharp Gaussian-like tails, making it a premier IXS spectrometer for studying the dynamics of soft materials, while also delivering competitive performance for investigating phonon dynamics in hard condensed matter systems, including a broad range of quantum materials.

43 PARTICLE ACCELERATORS↗
NASA NTRS1984

SMM observations of K-alpha radiation from fluorescence of photospheric iron by solar flare X-rays

High-resolution Fe K-alpha spectra near 1.94 A observed during solar flares with the Bent Crystal Spectrometer on the Solar Maximum Mission are presented. The evidence for two possible excitation mechanisms, electron impact and fluorescence, is examined. It is found that the fluorescence mechanism satisfactorily describes the results, while the observations do not support electron collisional excitation of the Fe K-alpha transitions in low ionization stages (II-XII) of iron. Using Bai's model of the fluorescent excitation process, the photospheric iron abundance relative to that of hydrogen is estimated to be 5-6 x 10 to the -5th. The mean height of the soft X-ray source producing the K-alpha fluorescence is calculated on the basis of this model for about 40 large flares. The solar K-alpha lines are found to be about 25 percent wider than those measured in the laboratory. Weak line features observed at wavelengths shorter than that of the K-alpha lines are discussed.

Parmar, A. N.↗
NASA NTRS1980

X-ray spectroscopy of late-type stars

The solid state spectrometer on the Einstein Observatory determined .4 - 4.5 keV spectra for Capella, Algol and 6 RS CVn binaries. All show evidence for a bimodal distribution of emission measure with temperature with one component approximately 7 million degrees and one approximately 40 million degrees. The spread in values of both luminosity and emission measure is 10 for the low temperature component and approximately 500 for the high temperature component. Line emission due to Fe can be identified in most of them and abundances of Si, S and Fe are consistent with approximately solar values in all cases. Estimates indicate dimensions of the emitting regions are on the order of the stellar size and the binary separation for the low and high temperature components, respectively, unless the pressures are high. Variations in the flux were observed, mostly in the hard component for the RS CVn binaries, in the soft component for Capella. A flare was observed during primary eclipse of Algol. The possibility is discussed that the other variations could all be due to intrinsic variability with a time scale of hours-days rather than eclipse or modulation with photometric phase.

Swank, J. H.↗
NASA NTRS1985

Soft X-Ray Telescope (SXRT)

The soft X-ray telescope (SXRT) will provide direct images of the solar corona with spatial resolution of about 1 arcsecond. These images will show the global structure of the corona, the location and area of coronal holes, and the presence of even the smallest active regions and flares. The good spatial resolution will show the fine scale magnetic structure and changes in these phenomena. These observations are essential for monitoring, predicting, and understanding the solar magnetic cycle, coronal heating, solar flares, coronal mass ejections, and the solar wind. These observations complement those of the White Light Coronagraph and Ultra-Violet Coronal Spectrometer; the SXRT will detect active regions and coronal holes near the east limb, thereby giving a week or more of advanced warning for disturbed geomagnetic conditions at Earth. The instrument consists of a grazing incidence collecting mirror with a full disk film camera at the primary focus, and a secondary relay optic that feeds a CCD camera with a field of view about the size of an average active region.

Moore, R. L.↗
NASA NTRS1986

Soft X-ray telescope (SXRT)

The soft X-ray telescope (SXRT) will provide direct images of the solar corona with spatial resolution of about 1 arcsecond. These images will show the global structure of the corona, the location and area of coronal holes, and the presence of even the smallest active regions and flares. The good spatial resolution will show the fine scale magnetic structure and changes in these phenomena. These observations are essential for monitoring, predicting, and understanding the solar magnetic cycle, coronal heating, solar flares, coronal mass ejections, and the solar wind. These observations complement those of the White Light Coronagraph and Ultra-Violet Coronal Spectrometer; the SXRT will detect active regions and coronal holes near the east limb, thereby giving a week or more of advanced warning for disturbed geomagnetic conditions at Earth. The instrument consists of a grazing incidence collecting mirror with a full-disk film camera at the primary focus, and a secondary relay optic that feeds a CCD camera with a field of view about the size of an average active region.

Moore, R.↗
NASA NTRS1985

The energy spectra of solar flare electrons

A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

Evenson, P. A.↗
NASA NTRS1980

IUE observations of a luminous M supergiant that exhibits emission continuum in the far ultraviolet

IUE observations of the late-type M supergiant star TV Gem which reveal an intense continuum in the far ultraviolet are discussed. TV Gem was observed in low dispersion in November 1979 and in high and low dispersion in January 1980 by the short and long wavelength cameras of the IUE spectrometer. An essentially featureless UV continuum was obtained, with the exception of a number of broad absorption features in the short wavelength region. A comparison with ground-based observations indicates that at wavelengths greater than 3200 A the continuum emission is essentially due to the M1 supergiant, while at shorter wavelengths the continuum is dominated by a hot companion. The UV continuum can be explained by a B9 or A1 III-IV early companion approximately 2 to 3 magnitudes fainter than the M1 supergiant, or by an accretion disk formed by mass transfer from the extended envelope of the M1 primary onto the surface of a highly condensed secondary. Soft X-ray observations from HEAO 2 are suggested as a means to investigate these interpretations.

Michalitsianos, A. G.↗
NASA NTRS1979

Rocket studies of solar corona and transition region

The XSST (X-Ray Spectrometer/Spectrograph Telescope) rocket payload launched by a Nike Boosted Black Brant was designed to provide high spectral resolution coronal soft X-ray line information on a spectrographic plate, as well as time resolved photo-electric records of pre-selected lines and spectral regions. This spectral data is obtained from a 1 x 10 arc second solar region defined by the paraboloidal telescope of the XSST. The transition region camera provided full disc images in selected spectral intervals originating in lower temperature zones than the emitting regions accessible to the XSST. A H-alpha camera system allowed referencing the measurements to the chromospheric temperatures and altitudes. Payload flight and recovery information is provided along with X-ray photoelectric and UV flight data, transition camera results and a summary of the anomalies encountered. Instrument mechanical stability and spectrometer pointing direction are also examined.

Acton, L. W.↗
NASA NTRS1980

High-resolution X-ray spectra of solar flares. IV - General spectral properties of M type flares

The spectral characteristics in selected narrow regions of the X-ray spectrum of class M solar flares are analyzed. High-resolution spectra in the ranges 1.82-1.97, 2.98-3.07, 3.14-3.24 and 8.26-8.53 A, which contain lines important for the determination of electron temperature and departure from ionization equilibrium, were recorded by spaceborne Bragg crystal spectrometers. Temperatures of up to 20,000,000 K are obtained from line ratios during flare rise phases in M as well as X flares, while in the decay phase the calcium temperature can be as low as 8,000,000 K, which is significantly lower than in X flares. Large nonthermal motions (on the order of 130 km/sec at most) are also observed in M as well as X flares, which are largest during the soft X-ray rise phase. Finally, it is shown that the method proposed by Gabriel and Phillips (1979) for detecting departures of electrons from Maxwellian velocity distributions is not sufficiently sensitive to give reliable results for the present data.

Feldman, U.↗
NASA NTRS1981

The Einstein Observatory and future X-ray telescopes

A history of the events leading to the development and flight of the Einstein Observatory is given. The advantages of using grazing-incidence telescopes for solar and extrasolar X-ray astronomy is first discussed and followed by a description of the HEAO program. The Einstein Observatory marks a departure from the manner in which X-ray investigations are carried out, from individual experiments to the shared use of large facilities. The Observatory has achieved a sensitivity to point sources of 10 to the -14th erg/sq cm-sec in the 1-3 keV band, a flux 500 times smaller than previously detected and about 10 million times smaller than that of the first extrasolar source detected in 1962. The design philosophy of the Observatory entails three principles: (1) the unified scientific approach, (2) the establishment of spacecraft requirements at lowest acceptable levels that still allow operating flexibility, and (3) the idea of 'soft' rather than 'hard' failure. The mirror design, including the high resolution imager, the imaging proportional counter, and the solid-state and focal plane crystal spectrometers, is also given. An account of the struggle to gain acceptance by the scientific community and the funding agencies of the need for the Einstein Observatory mission is discussed. Finally, results of observations made by the Observatory are presented in detail, along with plans for future observation experiments.

Giacconi, R.↗
NASA NTRS1982

The anomalous X-ray absorption spectrum of Vela X-1

The HEAO 2 satellite's Solid State Spectrometer and Monitor Proportional Counter was used to observe one orbit of the massive X-ray binary Vela X-1. Using spectral fits to the data as a function of orbital phase, the column density and state of the material along the line of sight to the X-ray source has been inferred. The spectrum near orbital phase 0.2 compares favorably with absorption by neutral material with a column density corresponding to plausible values of stellar wind velocity law and total primary mass loss rate. Spectra at later orbital phases, which show unexpected strong absorption features near 2.0 and 2.5 keV, are interpreted as due to absorption by material with suppressed opacity below 2.0 keV. The opacity required to produce the observed features implies either the presence of an intense soft X-ray flux, or altered elemental abundances in the gas near Vela X-1.

Kallman, T. R.↗
NASA NTRS1981

Photon-counting array detectors for space and ground-based studies at ultraviolet and vacuum ultraviolet /VUV/ wavelengths

The Multi-Anode Microchannel Arrays (MAMAs) are a family of photoelectric photon-counting array detectors, with formats as large as (256 x 1024)-pixels that can be operated in a windowless configuration at vacuum ultraviolet (VUV) and soft X-ray wavelengths or in a sealed configuration at ultraviolet and visible wavelengths. This paper describes the construction and modes of operation of (1 x 1024)-pixel and (24 x 1024)-pixel MAMA detector systems that are being built and qualified for use in sounding-rocket spectrometers for solar and stellar observations at wavelengths below 1300 A. The performance characteristics of the MAMA detectors at ultraviolet and VUV wavelengths are also described.

Timothy, J. G.↗
NASA NTRS1983

The states of Cygnus X-1

HEAO 3 High Resolution Gamma-Ray Spectrometer observations of Cygnus X-1 in the 48-300 keV range, along with correlated 3-6 keV Ariel 5 data, have led to the identification of a new state for this object with low flux in both the soft and hard X-ray regions. This is followed by a slow increase in the hard X-ray flux to the normal low state of the source, characterized by a low intensity soft X-ray emission and a high intensity hard X-ray emission. The new 'superlow' state is interpreted in terms of the Compton model, where the X-ray emission arises from the scattering of low energy photons and one-billion K hot electrons. The superlow state may be seen as one extreme of a continuum of low state behavior, given that Compton cooling should begin to quench the hot electrons at higher soft X-ray fluxes, giving rise to the softer X-ray spectrum and to the anticorrelation in changes in the soft and hard X-ray fluxes.

Ling, J. C.↗
NASA NTRS1984

High-resolution soft X-ray spectra of Scorpius X-1 - The structure of circumsource accreting material

Four observations of Scorpius X-1 with the Objective Grating Spectrometer of the Einstein Observatory have provided high-resolution spectra (lambda/Delta lambda = approximately 20-50) in the wavelength range 7-46 A. The spectra reveal the presence of absorption structure due to oxygen, nitrogen, and iron, and variable emission structure associated with ionized iron and nitrogen. The strengths of these features suggest that the N/O abundance ratio in the absorbing and line emitting gas is anomalously high, which might indicate that these spectral components are associated with processed material, probably accreting matter transferred from the surface of an evolved companion. Constraints on the inclination of the system, however, imply that this cool, dense, accreting material must be well out of the plane of the binary system. Possible models for the origin and nature of this circumsource medium are discussed. An extensive discussion of the calibration of the Objective Grating Spectrometer and of the analysis of spectra acquired by that instrument is also provided.

Kahn, S. M.↗
NASA NTRS1986

Spectral evolution in gamma-ray bursts

The Hard X-ray Burst Spectrometer (HXRBS) and the Gamma-Ray Spectrometer (GRS) on NASA's Solar Maximum Mission satellite have independently monitored cosmic gamma-ray bursts since launch in February 1980. Several bursts with relatively simple pulse structure and sufficient intensity have been analyzed for evidence of spectral variability on time scales shorter than the pulse durations. In many of these bursts pulse structures are found, ranging in duration from 1 to 10 seconds, which exhibit a trend of hard-to-soft spectral evolution. No significant evidence for soft-to-hard evolution has been found. The HXRBS data above 100 keV and the GRS data above 1 MeV indicate that the spectral evolution generally is not due to time-varying absorption features at energies below 100 keV.

Norris, J. P.↗
NASA NTRS1986

Results of a search for a new class of GRBS in the SMM data

The results of a search for the soft and short Gamma-Ray Bursts (GRBs) in the data of the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM) are presented. Data for four events are presented, including their time profiles and spectral characteristics. In one case the instrument time resolution reveals a total burst duration of 55 ms with rise and decay times of less than about 5 ms.

Kouveliotou, C.↗